1. Field
Example embodiments of the present invention relate to connectionless communications networks and more particularly to such networks in which bandwidth is shared between users.
2. Description of Related Art
One of the most significant problems affecting users of Internet Protocol Networks (IP Packet Networks) is a lack of guaranteed quality of service (QoS), such that while it is possible to make VoIP calls for example, packet delays may cause the quality of the call to be poor.
There is a further difficulty in that file sharing can cause delays in the initial establishment of a VoIP call because peer to peer file sharing networks will use all of the available bandwidth in order to try to speed up the transfer of files even although they may be of relatively low priority.
Thus congestion on the network is a significant difficulty particularly for two way VoIP or video calls because delayed or dropped packets cannot be re-sent since they only have a time-useful window of around 300 msec (voice). Consequently as network usage off the backbone or M-bone increases and localised wireless network schemes “piggy-back” on home routers, high priority or time-critical transmissions need to be protected.
There have been attempts to introduce protection for time critical transmissions but most involve complex modifications of routers and other network common equipment to perform. One example of this is to be found in EP0706297 which describes a method of controlling congestion in an ATM switch. In order for the method described in this specification each router in the network would require modification. The method provides a rigid congestion control scheme which would in practice have no effect on UDP:TCP traffic ratios and would simply be at maximum congestion where peer- to peer traffic was high.
Another known scheme is disclosed in US2004/0172464. This provides for the establishment of two QoS classes between two sites, in practice probably two linked business locations. The scheme is implemented by having an admission control algorithm at the two end points of the pipe between the two locations which effectively reserves a part of the pipe (effectively a virtual leased line) for real time traffic. There is a requirement for imposing a rigid QoS allocation and may be a requirement for Gateway or router modification at the two end points.
There are other solutions proposed to the problem of ensuring time critical packets over IP networks have priority including using underlying network bearers such as ATM or MPLS, using deep packet inspection techniques, service prioritisation, end-to-end congestion notification schemes and, in the extreme, over provisioning of the network.
All of these solutions have significant cost o complexity issues associated with them requiring changes to deployed routers or protocol modifications, moving the problem from the IP layer 9 which in turn reduces the advantages of using IP) or is costly when traffic flows rise. Deep Packet inspection methods have the additional disadvantage of failing to work when packets are encrypted.
Since most of the QoS issues in public IP networks arise from peer to peer traffic, the flows filling up to network capacity regardless of available bandwidth, operators face difficulties offering voice and video services without introducing a QoS scheme because P2P traffic will adversely affect these services without being particularly adversely affected themselves.